To further our understanding of the molecular etiology underlying common genotypic subsets of human CRC, and to assess the extent to which they recapitulate human disease in animal models, we amassed a collection of GEMMs that combine colon-specific mutations, including somatic alterations in Apc (ApcCKO), Tp53 (Tp53flox/flox), Kras (KrasLSL-G12D) and Braf (BrafV600E), genes that are among the most frequently mutated in human sporadic CRC (Cancer Genome Atlas Network, 2012). The gene discussed is KRAS; the disease is colorectal carcinoma.